Lithium iron phosphate batteries are turning up on more and more survey boats, often as a drop-in swap for the old lead-acid bank. They store more and weigh less, and they need protecting from themselves. A lithium cell taken outside its voltage, current or temperature limits can be ruined, and some failures end in fire. A battery management system watches those limits and disconnects the battery before they're crossed.
What the standard asks
ABYC E-13 is the lithium battery standard. Panbo's summary: it applies to systems of 600 Wh or more, which is 50 Ah at 12 V, built or installed since it took effect. Section 13.7 requires a BMS on every lithium battery. The notes recommend a signal before a disconnect so the crew isn't caught out. Manuals must state the charge and discharge limits and temperature limits. Restraint is stricter than for lead-acid: no visible movement.
E-13 doesn't set the disconnect thresholds. Those come from the battery maker, which is why the documents matter.
How a surveyor checks it
Find out what's installed: chemistry, make, capacity, and whether it's a drop-in battery with its own BMS or loose cells with an external one. Then what the BMS can do: disconnect charging, discharging or both, and whether anything warns before it does. A bank of loose cells with no BMS at all is the A.
Next, the charging sources. A charger or alternator set for lead-acid on a lithium bank is a common gap, and when a BMS disconnects under charge, an alternator can be left with nowhere to send its current. Ask for the installer's paperwork. A lithium system with no record of who fitted it or how it was set up is a B on its own, because nobody can say what it'll do at its limits.